Frogs by State

Frogs and Toads of Illinois

Frogs and Toads of Illinois


True Frog Family – Ranidae

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American Bullfrog (Lithobates catesbeianus)

The American Bullfrog is the largest native frog in the United States. There is no dorsal ridge that runs down its back on the American Bullfrog. This is the distinguishable characteristics of the frog.

Green Frog (Lithobates clamitans)

The Green Frog looks very much like the American Bullfrog but it’s a tad smaller. It has a dorsal ridge that runs down its back but they are incomplete and do not reach all the way.


The Wood Frog (Lithobates sylvaticus) is one of the most widespread frog in the United States but it’s a little rare in Illinois. It’s listed by the states as a Species in Greatest Need of Conservation. It’s fairly easy to distingush because of it’s mask around it’s eyes.

Crawfish Frog (Lithobates areolatus)

The Crawfish Frog gets its name from living in crawfish holes. Its has skin folds on the side and a small typanum. It also has a pair of vocal sacs for calling.

Plains Leopard Frog (Lithobates blairi)
Northern Leopard Frog (Lithobates pipiens)
Southern Leopard Frog (Lithobates sphenocephalus)

The Southern Leopard Frog has a white spot on its tympanum which can help differentiate the species from the other two. The Plains Leopard Frog is different from the Southern and Northern Leopard Frog because of its dorsal ridge. The Plains Leopard Frogs has a break and an indent near its butt while the North and South Leopard Frog just has a straight line.

Pickeral Frog (Lithobates palustris) photo by Brian Gratwicke

Pickeral Frog looks like the leopard frogs but its spots are more rectangular than the leopard frogs.

Tree Frog Family – Hylidae

Northern Cricket Frog

The Northern Cricket Frog is the only frog in the state. Its skin is relatively more rough than the other tree frogs in the state. It also has no distinct markings.

Eastern Gray Tree Frog and Cope’s Gray Tree Frog

These two frogs are identical besides their calls and chromosome numbers. Note that Gray Tree Frogs are not always gray and can be green. They have yellow or orange coloration on their back legs which is nice to identify them.

Bird-Voiced Tree Frog

The Cope’s Gray Tree Frog, the Eastern Gray Tree Frog and the Bird-Voiced Frog look very much a like. The difference is the coloration on the inner thigh. Cope’s Gray Tree Frog and Gray Tree Frog has brighter orange color on the thigh while the Bird-Voiced Frog is more greenish-yellow.

The Green Tree Frog does not have any coloration on its inner legs. It has a white line that runs down its side.

Spring Peeper

The Spring Peeper is a notoriously loud frog and one of the first signs of spring. It has a noticeable X marking on its back.

Boreal Chorus Frog

The Boreal Chorus Frog is found throughout the state besides the southern tip. The middle stripe on its back is occasionally broken. It also has really small legs.

Midland / Western Chorus Frog (Pseudacris triseriata)

The Midland or Western Chorus Frog is found in the Southern half of the state. The three stripes on its back are rarely broken.

Upland Chorus Frog

The Upland Chorus Frog is found on the southern tip of the state. The stripes on it’s back are often broken up and can appear as spots.

Illinois Chorus Frog

The Illinois Chorus Frog does not have a white line that extends off the lips while the other chorus frogs do.


True Toad Family – Bufonidae

The family Bufonidae is known for the toxins / poison they produce called Bufotoxins. It is a bad idea to try to eat these guys.

American Toad
Fowler’s Toad

The American Toad and Fowler’s Toad look fairly similar. The Fowler’s Toad has their cranial crest and the parotoid gland touch while the American Toad’s cranial crest and parotoid gland do not touch or are connected by a spur.

Spadefoot Toads – Scaphiopodidae

Eastern Spadefoot Toad

The Eastern Spadefoot Toad is the only Spadefoot toad in the state so it can easily be identified because of the spade on its back legs.

Narrowed Mouth Toad Family – Microhylidae

Eastern Narrowed Mouth Toad

The Eastern Narrow Mouthed Toad is the only narrow mouthed toad in the state. One could potentially misidentify it has a Spadefoot toad because of its burrowing lifestyle but the head is narrower and there’s no spade on the back feet.


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